ABC News(WASHINGTON) — A federal grand jury on Friday returned a new indictment against a dozen Russians as part of special counsel Robert Mueller’s investigation into alleged Russian meddling during the 2016 presidential campaign.

The latest indictment targets 12 Russian intelligence officers for engaging in a sustained effort to hack networks of Democratic Congressional Campaign Committee, the Democratic National Committee and Hillary Clinton’s campaign. All 12 are members of the GRU, Russia’s intelligence service.

In announcing the indictment, Deputy Attorney General described how Russians with the GRU began a “spearphishing” campaign in 2016 against volunteers and employees of Clinton’s campaign, including campaign chairman John Podesta.

Russians’ spearphishing techniques also earned them access to networks of the DCCC and DNC, where they were able to steal emails and documents; covertly monitor the computer activity of dozens of employees; and implant hundreds of malicious files to steal passwords and maintain access to the networks, according to the indictment.

Rosenstein described how “one GRU unit worked to steal information, while another unit worked to disseminate stolen information.”

The new indictment raises the stakes as President Donald Trump is preparing for a July 16 summit with Russian President Vladimir Putin in Helsinki. Already, Trump has fielded questions about whether he will raise the matter of Russian interference in the 2016 campaign, saying he expects Putin to continue to deny any involvement.

“All I can do is say, ‘Did you?’ And, ‘Don’t do it again,’” Trump told reporters during the recent NATO summit.

Former Gov. Chris Christie, a one-time Trump advisor and ABC News consultant, said Mueller wanted Trump to enter his meeting with Putin with this indictment in front of him.

“The unmistakable conclusion is that Bob Mueller wanted to show that this is not a debatable point,” Christie said. “There is no debate that the Russians meddled in the election.”

In just over a year since his appointment as special counsel, Robert Mueller and his hand-picked team of prosecutors have filed nine indictments covering twenty individuals and three businesses, earned five guilty pleas, have two criminal cases headed to trial, and sentenced one person to prison.

President Donald Trump and his supporters have repeatedly called Mueller’s investigation a “Witch Hunt.”

Friday’s indictment comes as Rosenstein faces increased scrutiny from President Trump’s backers on Capitol Hill. House Republicans have threatened to hold Rosenstein in contempt of Congress for what they say is the Justice Department’s failure to comply in a timely manner with a subpoena for documents related to the Clinton email and Trump-Russia investigations.

The Department of Justice last Friday sent a letter to two House committees insisting it had fully complied.